A separations problem which has required and received considerable attention is that of separating unsaturated aliphatic hydrocarbons such as olefins from close boiling and difficulty separable saturated aliphatic hydrocarbons such as paraffins. Many processes have been proposed for such separations including liquid-liquid extraction, extractive distillation, as well as complex formation. With respect to complex formation, various complexing reagents have been described in the prior art. However, difficulties exist with the previously known systems. For example, aqueous systems involving copper (I), hereinafter denoted as (Cu(I)), salts and ammonia or ammonium are corrosive and lack necessary long term stability. Non-aqueous Cu(I) solutions using a pyridine solvent have proven difficult to handle due to the solvent and require large scale systems because the reagent is in the form of a slurry in the solvent. Cu(I) sulfonic acid reagents have proven too viscous for easy handling;
furthermore the strong heats of absorption of these salts for olefins render the decomplexation difficult. Complexing reagents formed from Cu(I) salt and Lewis acid systems disclosed in the prior art have evidenced solubility problems and solvent alkylation problems.
Several examples of Lewis acid-free Cu(I) reagents are known. Prior art has disclosed a Cu(I) oxalate system and a Cu(I) fluorinated acetylacetonate system. Both of these systems, although active for ethylene complexation, possess enough drawbacks to render them unattractive for commercialization. The oxalate compound suffers from insufficient solubility while the acetylacetonate system appears to exhibit less than ideal stability in addition to high ligand cost.
There exists therefore, the need for a complexing reagent which has a high olefin complexing capacity while providing for easy desorption of the olefin, has a high solubility in an inert solvent, has a favorable viscosity, is relatively stable, gives few side reactions during the complexing process, and can be prepared from cheap starting materials.
It is an object of this invention to provide complexing agents for separation of olefins from paraffins which exhibit good olefin complexing capacity and easy reversibility, and are soluble in inert solvents.
It is also an object of this invention to provide a method for preparing such complexing reagents from relatively inexpensive starting materials.
It is also an object of this invention to provide a method for separating olefins from a mixture of olefins and paraffins by using the aforementioned complexing reagents.